Determination of imidacloprid and benzimidazole residues in fruits and vegetables by liquid chromatography-mass spectrometry after ethyl acetate multiresidue extraction

A simple and sensitive method based on liquid chromatography-atmospheric pr essure ionization-mass spectrometry is described for the determination of 4 benzimidazoie pesticides (carbendazim, thiabendazole, benomyl, and thiopha nate-methyl) and imidacloprid in vegetables and fruits. Food samples were t ypically extracted with ethyl acetate to draw the analytes into the organic phase, No cleanup step was necessary before injection into the liquid chro matographic (LC) system with electrospray mass spectrometric detection, The analytes were separated on a reversed-phase C8LC column, Limits of detecti on for the compounds were in the mu g/L range. Results are reported for val idation studies with fortified pear and tomato samples and for residues of the target compounds found in the pesticide residue monitoring program duri ng 1998.